B. Chaudret and R. Poilblanc, Organometallics, 1985, 4, 1722-1726 report the synthesis and characterization of a ruthenium complex, RuH.sub.6 (PCy.sub.3).sub.2, later formulated as RuH.sub.2 (H.sub.2).sub.2 (PCy.sub.3).sub.2 by T. Arliguie et al., Inorg. Chem., 1988, Vol. 27, 598-599. The complex was prepared from Ru(COD)(COT). (COD is 1,5-cyclooctadiene, COT is 1,3,5-cyclooctatriene and Cy is cyclohexyl).
A.M. Joshi et al., Prog in Catal., 1992, 73, 143 describe nitrile hydrogenations using di- and tri-nuclear Ru(II) complexes containing chelating diphosphines such as 1,4-bis(diphenylphorphino)butane (dppb). They disclose a preference for [RuHCl(dppb)].sub.3 for nitrile hydrogenations.